Drastic reductions in Arctic sea ice in the last decade may be intensifying the chemical release of bromine into the atmosphere, resulting in ground-level ozone depletion and the deposit of toxic mercury in the Arctic, according to a new NASA-led study.
The connection between changes in the Arctic Ocean's ice cover and bromine chemical processes is determined by the interaction between the salt in sea ice, frigid temperatures and sunlight. When these mix, the salty ice releases bromine into the air and starts a cascade of chemical reactions called a "bromine explosion." These reactions rapidly create more molecules of bromine monoxide in the atmosphere. Bromine then reacts with a gaseous form of mercury, turning it into a pollutant that falls to Earth's surface.
Bromine also can remove ozone from the lowest layer of the atmosphere, the troposphere. Despite ozone's beneficial role blocking harmful radiation in the stratosphere, ozone is a pollutant in the ground-level troposphere. A team from the United States, Canada, Germany, and the United Kingdom, led by Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, Calif., produced the study, which has been accepted for publication in the Journal of Geophysical Research Atmospheres. The team combined data from six NASA, European Space Agency and Canadian Space Agency satellites; field observations and a model of how air moves in the atmosphere to link Arctic sea ice changes to bromine explosions over the Beaufort Sea, extending to the Amundsen Gulf in the Canadian Arctic.